My goal with this project was to create a magical crystal ball that will allow the recipient to see into their future.  My solution was to create a self contained, battery powered ball that uses an accelerometer to detect when it is shaken and then trigger a relevant image to be displayed on an LCD screen.

I found a 1.8" LCD screen mounted on a MicroSD card breakout board which was perfect since it allowed me to easily store and display images.  Due to size constraints I needed to make a custom PCB with surface mount components.  The circuitry is pretty simple, just an ATmega328 microcontroller hooked up to the battery, the display, and the accelerometer. I used an LIS3DH accelerometer due to its interrupt capabilities.  

 

Power consumption was a major concern since it needs to be partially disassembled to be charged so this should happen as rarely as possible.  This was optimized by putting the microcontroller and display into deep sleep mode until an acceleration above a set threshold caused the accelerometer to trigger an interrupt.  The microcontroller and display would then wake up, load and display an image for a few seconds, and go back to sleep.  Based on measured current draws I calculated that the 1000mAh battery should last almost 5 months under normal usage!

I found a half-sphere glass magnifier on Amazon that worked perfectly for the top half of the ball and had the added benefit of magnifying the LCD display, making the small screen look more impressive.  I then designed the rest of the ball around the glass piece and the electronics.  The glass is pretty heavy so I included a steel counterweight to balance the weight distrubution and make the overall feel what you would expect for a crystal ball of that size.

 

I wanted the design to be seamless and spherical while also not being permanently attached together so I came up with a design where the parts screw together.  The electronics mount onto the center piece which is threaded on the outside.  The two outer pieces (a top ring to hold the glass in place and a bottom piece containing the counterweight) both screw onto the center piece until they meet in the middle forming a tight seam.  I originally wanted the body to be 3D printed out of metal but found that the tolerances I needed for the threads weren't possible so I had to settle for plastic.  I ordered high quality 3D prints from Sculpteo and it was quite the relief when they arrived and the thread design worked!